This invention is related to a negative type photosensitive resin composition containing a phenol/biphenylene resin and a method for forming of a resist pattern using the negative type photosensitive resin composition.
Due to its high reliability, epoxy resin composition containing epoxy resin and phenol resin has been widely used as a sealing material for semiconductor devices, such as IC and LSI. Recently, a photosensitive resin composition containing both epoxy resin and phenol resin has been proposed to replace the conventional phenol resin for the formation of resist in the manufacturing process of WL-CSP (wafer level chip size packaging) to achieve good physical properties. The photosensitive resin composition usually contains cresol/xylenol novolac resin, epoxy resin, melamine resin, as well as a photosensitive component.
In terms of forming a pattern through exposure and development, the photosensitive resin composition is able to provide sufficient photolithographic performance. However, the physical properties of the resin pattern formed by the photosensitive resin composition are not sufficient and the resin pattern is unable to withstand the reliability test and heat-impact resistance test required for a permanent resist.
Generally, an epoxy resin with a high molecular weight (the higher the epoxide equivalent, the longer the distance between the structural core) can be used alone or added to a resin composition to increase the heat-impact resistance of an insulating resist based on a hardened resin material. For the purpose of photolithography, however, it is very difficult to use an epoxy resin with a high molecular weight due to the difficulties in the development process using an aqueous alkaline solution. Therefore, it is highly desirable to develop a photosensitive resin composition, which has excellent photolithographic performance as well as sufficient heat-impact resistance of the hardened resin pattern.